Solar System

The Mars Exploration Rovers are wrapping up another year of exploring their seventh -- having experienced both the best of times and the worst of times: Spirit continued a 10-month struggle to endure its coldest, harshest Martian winter yet; Opportunity set a new record for driving despite an arthritic front wheel and a broken shoulder, putting more miles on her rocker bogie in 2010 than in any other single year.

SOHO was launched more than 15 years ago to study the Sun, primarily; but a side benefit of its constant observation of the Sun has been its ability to notice "sungrazers," comets that are on deadly close approaches to our star.